This proposal is concerned with providing scientific training of the Candidate while developing a comprehensive understanding of the embryonic/maternal factors affecting embryo viability in vivo in felids. In vitro fertilization (IVF) and embryo transfer have the potential to substantially benefit the propagation of cats for research and conservation. However, efficient application of these techniques is hindered by a lack of knowledge about the proper maternal environment needed to support embryo and fetal development and how to simulate these conditions in embryo transfer recipients. In this proposal, the maternal environment of gonadotropin-treated recipients will be investigated using a systematic approach, focusing on: i) the pharmacokinetics and physiological effects of exogenous gonadotropins; ii) the histological characteristics of corpora lutea (CL), oviducts and uteri; and iii) endocrine traits including circulating hormone concentrations and CL luteinizing hormone receptor and progesterone content. By interrelating these factors and comparing results with a recently established reproductive database for naturally-estrous, mated cats, the most 'normal' embryo recipient type will be identified. The physiological suitability of the selected recipient type to support embryo/fetal development and the viability of IVF embryos at different developmental stages will be assessed to identify an optimum embryo transfer strategy. The new information will be used in related studies to: i) propagate feline animal models of human disease; ii) examine embryo viability following cryopreservation; iii) develop a new research animal model, monozygotic twins; and iv) begin using IVF and embryo transfer to conserve endangered felids. this proposal describes a multidisciplinary research approach that will allow the Candidate to develop a comprehensive understanding of fertility while promoting his career advancement as a specialist in reproductive physiology of laboratory and rare felids. The Candidate will receive extensive training in fundamental research concepts and sophisticated biotechniques including radioreceptor- and radioimmunoassay, DNA 'fingerprint' analysis, embryo micromanipulation and cryopreservation. Funding of this proposal will allow the Candidate to exploit currently available resources at 5 major research institutions and acquire training from 7 established investigators. Research benefits will include: i) determining the embryonic and maternal factors affecting reproductive success; ii) increasing the limited database on felid reproduction; iii) generating a new animal model for research; iv) promoting genetic resource banking for managing felids; and v) enhancing the propagation of rare and endangered felids.